Glenn Tinseth developed a formula to calculate IBU's, which is referred to as the Tinseth formula. There are also Rager and Garetz which calculate IBU's. Different brewers use different formulas for calculating IBU, we use Tinseth here for the most part.

I am still confused as to why there are different scales for "International" Bittering Units. The article you referenced states: "one IBU is defined in terms of a metric measurement of one milligram of iso-alpha acid per liter of beer"

That seems pretty straightforward. The Tinseth scale seems to run numerically about 50% higher than other calculations for the same bitterness level hop addition.

What am I missing?

Last edited by Primavera on 26 Mar 2015, 00:28, edited 1 time in total.

Bitterness really boils (pun intended) down to taste. If you are trying to clone a recipe, it could take several attempts to get the bitterness right. A 90 minute boil is recommended and adding the bitterness hops at 60 minutes, if not, some hops get bound up in the early stages of the boil with proteins, including first wort hops, so you would probably end up using more hops to compensate.

This may be a little off topic, but....
I am somewhat bemused by people's firm belief in calculating the bitterness of their beer using a form of voodoo, ie a calculation based upon what?
Don't even start me on the hop utilisation factor in these equations. You could drive a bus through tHis if you are looking for accuracy or repeatability. Could be good for a PhD.

IBU are a measurement! The only accurate way to know the bitterness in beer is to M E A S U R E it.

Who provides the alpha acid content of the hops they are using?
The merchant.
Why does he provide an alpha acid content?
So he has a basis to charge for his product.
How is it possible that an entire annual crop of an agricultural product has the same acid content? How is it that two flowers have the same content?
Simply, it is not possible. At best, it is an average, and basing accurate calculations on averages is a recipe for disaster or fooling yourself.

So work around what you like and differences are probably natural variation due to averaging and not due to actual differences in calculations.

[EDIT: I like Lemon's rant which he wrote while I was writing this. There is a lot of truth to his rant.]

In the first post of this thread PV, you asked to be pointed to a good source in this area. This forum, is about the only place you will get quality info on the very tricky area of IBU's. I think your real question though is better articulated in your last post above where you wrote...

Primavera wrote:I am still confused as to why there are different scales for "International" Bittering Units. The article you referenced states: "one IBU is defined in terms of a metric measurement of one milligram of iso-alpha acid per liter of beer"... What am I missing?

I am going to try and answer that...

Firstly, your confusion/bewilderment in this area means you are on the right track and ae asking the right questions. Very few peope do this. You are naturally looking for some logic in this area (e.g. a certain beer should have the same "IBU's" no matter what) but unfortunately there isn't much logic here. Let's break things down a little...

Measured (Actual) IBU's - Laboratory and Perceived

Measured or actual IBU's [my terminology] are those based on taking measurements of an actual beer. This can be done in two ways:-

1. Laboratory Measurement: The beer can be put through a laboratory process and the alpha acids etc., measured with laboratory equipment. (I'm a bit rusty here but I think the laboratory measurement is not 1 milligram of iso-alpha acid per litre. I think John Palmer mentions how this definition is wrong in one podcast but I have forgotten now.) Even taking laboratory measurements can be tricky as far as I am aware believe it or not.

2. Perceived Measurement of IBU's: Let's take the same beer above and then give it to ten people to 'guess' the bitterness. Let's say that the laboratory measured the beer at 30 IBU's. Our panel of ten, hopefully, on average would agree with 30 IBU's but some hopping techniques such as first wort hopping, might make our panel estimate that abeer to be actually 27 IBU's.

So, that is our first problem. A laboratory measurement doesn't necessarily reflect how bitter the beer will taste. Our second problem (and biggest one) comes to estimating IBU's of a beer before we brew it...

When formulating a recipe, we need some sort of tool to make sure we get in the ball-park of bitterness we want. The only tools we have for that are mathematical formulas and they are very primitive. Some of the logic in some of the formulas is very flawed but they are still used. Some common formulas are known as Garetz, Rager and Tinseth. Tinseth is regarded as the best formula for all-grain beers and Rager for extract beers.

What you are having trouble accepting is how widely the estimates vary by and you are right. The variances are ridiculous. (Pretty sure I have used that exact word several times on this site when talking IBU's as it is ridiculous.) mally gave you a link above to a picture that shows the wide variances. I'm going to post a similiar picture again in this post so as it is clear to all readers just how wide a variance three IBU estimate formulas can give on the same recipe.

This whole problem is perpetuated by...

Almost no education this area is severely compounded by forum posts, books, software, recipe reports. magazine articles etc. Pretty much all of these state authoritatively, something like, "This recipe will give you 27.5 IBU's". There are so many things wrong with this most common of statements it's hard to know where to begin.

Firstly, it leads new brewers (who become old brewers) to believe that IBU's are definite numbers that can be easily predicted and measured. Old brewers believe this myth and pass it on. Secondly, the statement does not say how the IBU's were derived. Was it laboratory, perceived or from a formula? If it was from a formula, which software was used? (A lot of software actually uses incorrect formulas just to make things more messy.) And, if a formula was used, the recipe will not give brewer B the same IBU's as Brewer A unless A and B adjust for differences in their respective 'Volumes of Ambient Wort'. (See Clear Brewing Terminology)

Lemon's rant probably comes into play a little here. I'm going to put it another way... "Treat numbers as tools not Gods."

PP

And here is a pic of how much the IBU estimate formulas vary on the same recipes...

You do not have the required permissions to view the files attached to this post.

Last edited by PistolPatch on 26 Mar 2015, 17:43, edited 1 time in total.

If you have found the above or anything else of value on BIABrewer.info, consider supporting us by getting some BIPs!

I make things for a living. Very precise things that can be measured using different measurement systems, but each system is describing the same thing. It is repeatable and we know the capabilities, limitations and variability in our measuring equipment.

It seems that, at best, IBU's are an estimate with no universally accepted standards. So what happens if I want to clone a commercial beer? Stone lists their IPA as "IBUs: 77". What scale are they using? Does it even matter as it sounds like the variables in material and processes will overwhelm the result.

I like hoppy beers but find some of the highly hopped commercial beers undrinkable. I think they go to extremes more for bragging rights than for making a great product "Our ale has 100+ IBU's" might appeal to mouth surfers much the way Dave's Insanity hot sauce appeals to those who like to boast about their capsaicin tolerance. Do I shoot for a "65"? A "52"?

So, my take from this: Keep data on hop variables, try to find some combination you like, stick with it. Repeat as necessary until you have built up a toolkit of styles.

This is going to be a trip.

Last edited by Primavera on 26 Mar 2015, 19:48, edited 1 time in total.

The logic in here is precisely the reason I don't understand the "cloning" culture. I mean, I do respect anyone willing to ask questions while taking the time to smooth out as many variables as possible, but for me such time is better spent perfecting my own recipes.

There is value in the IBU calculations, though. A community such as this one, once the members become familiar with one another's methods ... we know how to recreate THEIR recipes to a much higher degree. I stressed about this topic very early on in my brewing hobby, but now I see what Tinseth will bring to my tongue.

Frustrating, yes ... but as long as you stick with one calculation, whichever it may be ... it will become rather predictable.

As primavera says ... who knows what Stone is using. Even if we had the answer, there are about 1000 more questions I have for them if I'm going to "clone" one of their beers. What they release to the public offers a decent starting point, but the finer details can be figured out with experience and tasting the product.

In a post above I explained the problems with estimating bitterness but what about flavour and aroma?

I think that is the question at least some of us might be asking. I'll come back to this.

Are you copying a recipe or designing/improving your own?

If you want to copy the flavour and aroma of someone else's recipe, you'll be battling (one exception) because it is very unlikely you will get enough information. Read this. The BIABacus is the exception but only if you are copying from a BIABacus file where the user has completed Section G.

If you are designing your own recipe, then you need experience and knowledge that I won't go into here.

If you are improving on your own recipe, then you must ask yourself, "Do I want more bitterness, flavour or aroma?" If you want more or less bitterness then that is a very easy problem to solve - more or less hops early in the boil.

Getting back to flavour and aroma

Lots of things to note here....

1. The bullshit: You've gathered that already I think PV. You see a whole lot of theorising, a massive focus on IBU 'adjustments' and too many other things to mention but are irrelevant or unimportant to adding flavour or aroma.

2. The total lack of experimentation and testing: I've done a lot of side by side testing and wish I had time to do more. To cut a long story short, I see no or very poor controls in brewing experiments. See "Basic Experiment" below.

3. Work out what you want: If you want more flavour or aroma, what flavour/s aroma/s do you want? Should you be looking for hops that are designed for what you want?

4. If you have it all worked out: Then, you can use software like the BIABacus too very easily increase or decrease flavour/aroma contributions.

Basic Experiment

As I can brew two "double-batches" simultaneously, if I had time, this is what I would do. (Anyone is welcome to come and use my gear to do this. I just have no time atm)

Design an IPA recipe as that is an extreme bitterness/flavour/aroma beer. In Kettle A, put all hops in at 75 minutes. In Kettle B, put all hops in at flame-out. Rack first half of Kettle B into a 'cube'. After first rack (5 mins after boil) apply immersion chiller.

I'd be left with 2 x 22.5L of "bitter" beer, 22.5L of "slow-chilled" beer and 22.5L of "actively-chilled beer."

I'd pitch/ferment them within a day of each other, let them ferment and then I'd taste them. And, I'd learn so much so quickly!!!!

But, what if both beers from the above experiment were terrible?

That used to be my fear and, in the past, prevented me from doing experiments I should have. There was no way I would have ever done an experiment that would result in a beer I could not drink.

The answer is blending. The experiment above is a classic example of how that works. Kettle A beer would probably be awfully bitter. Kettle B beer might be okay??? The point is that if either one is out of balance, there is nothing stopping you from blending it.

Wish I'd learned about blending years ago!!!!

If you have found the above or anything else of value on BIABrewer.info, consider supporting us by getting some BIPs!

Hey Primavera, I just reread this post for...probably the third or fourth time in the past couple or three weeks.

I've been doing studying and research on hops and hopping...hoping to ascertain a greater level of understanding. If interested, believe my posts are in the hops or hopping sections on this website.

From one of your posts on this you mentioned Stone's IPA. Most likely Stone Brewing is not just relying on IBU formula estimate (i.e. "Tinseth"). They certainly use a formula estimate, but most likely have each batch tested as well. Most of the larger breweries do that, and many smaller ones too.

Have you ever paid to send your beers in for IBU testing? I have...and posted the results here on biabrewer.info. It's interesting. And one other thing that I've posted about, if we take the AA listed on Hop packaging, there will be some big surprises...and most likely large undershooting of bitterness. Do you adjust the AA listed on your hops, or do you take it that hops still have the amount shown on packaging?

I list (for each of six beers) what was listed for AA on each Hop, and what I adjusted it to... Then showed what the Tinseth formula from the BIABacus said the IBU score should be. Then what actual testing showed the IBU on these beers to be. At a minimum, it was an exercise you would likely find interesting.